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pychu [463]
3 years ago
5

A woman 5.5 ft walks at a rate of 6 ft/sec towards a street light that is 22 ft above the ground. At what rate is the length of

her shadow changing when she is 15 ft from the base of the light?
Physics
2 answers:
Soloha48 [4]3 years ago
7 0

Answer:

The length of her shadow is changing at the rate  -2 m/s

Explanation:

Let the height oh the street light, h = 22 ft

Let the height of the woman, w = 5.5 ft

Horizontal distance to the street light = l

length of shadow = x

h/w = (l + x)/x

22/5.5 =  (l + x)/x

4x = l + x

3x = l

x = 1/3 l

taking the derivative with respect to t of both sides

dx/dt = 1/3 dl/dt

dl/dt = -6 ft/sec ( since the woman is walking towards the street light, the value of l is decreasing with time)

dx/dt = 1/3 * (-6)

dx/dt = -2 m/s

sveticcg [70]3 years ago
5 0

Answer:

Explanation:

By applying similar triangles rule,

22/5.5 = (x + s)/s

s = 5.5/22 × (x + s)

ds/dt = 5.5/22 × (dx/dt + ds/dt)

16.5/22 × ds/dt = 5.5/22 × dx/dt

16.5/22 × ds/dt = 5.5/22 × -6

ds/st = -2 ft/s.

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What can you infer from the fact that metals are good conductors of electricity?
LuckyWell [14K]

Answer:

Knowing that these metals are infact good conductors of electricity we can infer that metals are able to hold and conduct certain temperatures. Another thing we can infer is that these good conductors can be used in connection to transferring energy or electricity.

6 0
2 years ago
Read 2 more answers
1. A sprinter races in the 100 meter dash. It takes him 10 second to reach the finish line
poizon [28]

Answer:

v = 10 m/s

Explanation:

Given that,

Distance covered by a sprinter, d = 100 m

Time taken by him to reach the finish line, t = 10 s

We need to find his average velocity. We know that velocity is equal to the distance covered divided by time taken. So,

v = d/t

v=\dfrac{100\ m}{10\ s}\\\\v=10\ m/s

Hence, his average velocity is 10 m/s.

6 0
3 years ago
xConsider the following reduction potentials: Cu2+ + 2e– Cu E° = 0.339 V Pb2+ + 2e– Pb E° = –0.130 V For a galvanic cell employi
slega [8]

Answer:

Approximately \rm 90\; kJ.

Explanation:

Cathode is where reduction takes place and anode is where oxidation takes place. The potential of a electrochemical reaction (E^{\circ}(\text{cell})) is equal to

E^{\circ}(\text{cell}) = E^{\circ}(\text{cathode}) - E^{\circ}(\text{anode}).

There are two half-reactions in this question. \rm Cu^{2+} + 2\,e^{-} \rightleftharpoons Cu and \rm Pb^{2+} + 2\,e^{-} \rightleftharpoons Pb. Either could be the cathode (while the other acts as the anode.) However, for the reaction to be spontaneous, the value of E^{\circ}(\text{cell}) should be positive.

In this case, E^{\circ}(\text{cell}) is positive only if \rm Cu^{2+} + 2\,e^{-} \rightleftharpoons Cu is the reaction takes place at the cathode. The net reaction would be

\rm Cu^{2+} + Pb \to Cu + Pb^{2+}.

Its cell potential would be equal to 0.339 - (-0.130) = \rm 0.469\; V.

The maximum amount of electrical energy possible (under standard conditions) is equal to the free energy of this reaction:

\Delta G^{\circ} = n \cdot F \cdot E^{\circ} (\text{cell}),

where

  • n is the number moles of electrons transferred for each mole of the reaction. In this case the value of n is 2 as in the half-reactions.
  • F is Faraday's Constant (approximately 96485.33212\; \rm C \cdot mol^{-1}.)

\begin{aligned}\Delta G^{\circ} &= n \cdot F \cdot E^{\circ} (\text{cell})\cr &= 2\times 96485.33212 \times (0.339 - (-0.130)) \cr &\approx 9.0 \times 10^{4} \; \rm J \cr &= 90\; \rm kJ\end{aligned}.

5 0
3 years ago
When you rub a plastic rod with fur, the plastic rod becomes negatively charged and the fur becomes positively charged. As a con
Yuri [45]

Answer: C. the rod gains mass and the fur loses mass.

Explanation:Atomic particles have mass. The electron has a mass that is approximately 1/1836 that of the proton and with exchange exchange of charge this is also factored in. The movement of effect described above is known as the triboelectic charging process—charging by friction—which results in a transfer of electrons between the two objects when they are rubbed together. Plastic having a much greater affinity for electrons than animal fur pulls electrons from the atoms of fur, leaving both objects with an imbalance of charge. The plastic rod would have an excess of electrons and the fur has a shortage of electrons. Having an excess of electrons, the plastic is charged negatively and has more mass. In the same vein, the shortage of electrons on the fur leaves it with a positive charge and consequently with lesser mass.

4 0
3 years ago
For 1983 through 1989, the per capita consumption
Tresset [83]

Answer:

y = 43.55 + 2.15t

Explanation:

We were told that in 1983, the per capita consumption was 37.1 pounds, and in 1989 it was 50 pounds.

If we assume t = 0 corresponds to year 1980. Then, for 1983 it will be t = 3 and for 1989,it will be t = 9.

Thus, expressing the information as ordered pairs, we have; (3,37. 1) and (9,50).

Let us now find slope of the linear function:

m1 = (y2 - y1)/(t2 - t1)

m1 = (50 - 37.1)/(9 - 3)

m1 = 2.15

So, we can find the linear equation as;

y - 37.1 = 2.15(t - 3)

y = 37.1 + 2.15t - 6.45

y = 43.55 + 2.15t

8 0
3 years ago
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